Stubtest: ignore a new protocol dunder (python#16895)

This is added to all protocol classes on Python 3.12.2+ (it was added in
a patch release of 3.12 as part of a bugfix). There's no reason why
you'd want to explicitly include it in a stub (and doing so would lead
the type checker to incorrectly conclude that you wanted a member
literally called `__non_callable_proto_members__`)

Cf. python/typeshed#11384 and
python/typeshed#11383

(cherry picked from commit 517f5ae)

mypy/stubtest.py

@@ -1486,6 +1486,7 @@ def verify_typealias(
         # Added to all protocol classes on 3.12+ (or if using typing_extensions.Protocol)
         "__protocol_attrs__",
         "__callable_proto_members_only__",
+        "__non_callable_proto_members__",
         # typing implementation details, consider removing some of these:
         "__parameters__",
         "__origin__",